Conventionally, in the state of the art, a switching node has peripheral devices (connection devices for subscribers or lines), a central computer platform, a message distribution device, and other central units (coupling field, protocol termination devices (e.g., #7), background memory and operating devices). These relationships are shown in FIG. 1.
For reasons of fail-safe reliability, the central components of a switching system are designed to be redundant (i.e., doubled), while the peripheral devices are generally not structured to be redundant. In the case of increased failure requirements (e.g., rescuing stable connections beyond the failure of a peripheral device), however, the latter can demonstrate redundancy.
If signaling and voice are carried in a disassociated manner, on separate paths, and if the only task left to the peripheral devices is that of protocol processing and/or conversion without any physical termination of the voice channels, the restrictions of the peripheral devices with regard to the resource pool and the number of terminable voice channels are eliminated. The peripheral device is determined for this use, with regard to its capacity, by the performance capacity of the processors, the size of the memory and the capacity of the message interface.
Since more than one direction must be made available for connecting voice between the A subscriber and any B subscriber, two different peripheral devices PE are generally involved in establishing and ending the connection (FIG. 2).
A conventional peripheral device terminates the connection lines for which it has the responsibility of handling the switching technology processing. Usually, there are peripheral devices for terminating n PCM segments (e.g., n=4 PCM30 segments for 120 connection lines). In the present use, in which voice is transmitted outside the peripheral device, the restriction concerning the physically determined maximum number of terminable connection lines is eliminated. For this use, a peripheral device can process more than 120 connections at the same time, for example. These relationships are described in the European patent application EP 99123208.3. According to this application, such a peripheral device can run several times virtually on a real peripheral device, thereby creating the functionality of the connection control of n times 120 connections on a real peripheral device, for example. A network scenario in which switching centers are used for connections carried outside the switching center is shown in FIG. 3.
The switching center that acts to control connections made outside the switching center can make known subscriber or network features available to the A and/or B side subscriber of conventional TDM networks. This includes, in particular, announcements and dialogs that become necessary in certain situations (e.g., “this number is not in use,” “the number has changed: the new number is 722-25940” or an inquiry concerning authorization to dial into a packet network). In a conventional case, in which the working channel of the connection is passed into the switching center, these announcements and dialogs can be provided by peripheral devices equipped with the appropriate functionality.
However, if the working data is transmitted in a packet network outside the switching center, preferably an external system is used for this purpose. This system possesses interfaces to the packet network for the working data consisting of announcements and user input. Furthermore, the external announcement and dialog system (hereinafter referred to as the “IVR system” or “Interactive Voice Response system”) possess a logical control interface to the switching center that acts to control connections in the packet network transmitted outside the switching center.
The set of problems resulting from this is how to achieve control of an external system providing announcements and dialogs in a switching center that acts to control connections in the packet network transmitted outside the switching center. For this purpose, the announcement and dialog functions known from conventional switching centers are supposed to be available for connections carried by way of a packet network (i.e., standard announcements, announcements with variable content, dialogs with DTMF input or voice input of the end subscriber). Furthermore, it is supposed to be possible to use the connection control logic (Call Control) available in a conventional switching center to control the announcement and dialog function. Further, it should be passible to transmit working data freighted with announcements and subscriber input in the packet network, without the working data freighted with announcements and subscriber input being transmitted to the switching center responsible for control of connections carried outside the switching center.
Likewise, unnecessary conversion of the working data stream freighted with announcements and subscriber input to the TDM technology should also be avoided, such as the TDM connection technology in the peripheral units of the switching center active for connections carried outside the switching center. In the end, the availability of features and services of a conventional switching center, which require announcement and dialog functions, must be assured for the switching center for control of connections carried within the packet network, with little development effort or expense.
Conventionally, to solve these problems, announcements and dialogs are made available in the packet network by means of external systems. For this purpose, the announcements and dialogs are to be made available either at the network transition between the packet network and the TDM network or by means of packet-based IVR systems specifically designed for announcement and dialog functions. In this connection, control of the announcement and dialog function takes place by means of the call control server that controls the connection.
The advantage here is the general usability in packet networks, as well as the fact that no superfluous TDM equipment has to be provided and no required additional conversion of working data has to occur.
However, there is insufficient controllability/usability of the IVR function present in the packet network by means of a switching center active for connections carried in the packet network.